The perirhinal cortex (PR) and adjacent lateral amygdala (LA) are implicated in learning and emotion as well as certain disorders such as Alzheimer's disease, epilepsy, and schizophrenia. To understand the roles of these brain structures in learning and emotion, and the manner in which they might become compromised during aging or in disease states, one must know more about the properties of their neurons and synaptic interconnections. Preliminary data suggested a specific and testable working hypothesis about how the cellular and synaptic properties of neurons in PR and LA might combine to produce aspects of the emotional learning in which these brain regions are thought to participate. To evaluate and develop further the working hypothesis requires (i) collection of the requisite physiological and anatomical data describing the properties of PR and LA neurons; (ii) physiological and pharmacological characterization of their synaptic interconnections; and (iii) incorporation of these data into computational models. The experimental and modeling results will test certain cellular- and circuit-level mechanisms implicit in the working hypothesis. It is expected that the principles revealed in these computational models will generalize to other brain regions as well. This laboratory has already applied several useful and powerful methods to rat brain slices containing PR and LA-- including whole-cell recordings from visually preselected neurons, confocal microscopy, and serial anatomical reconstructions of recorded cells. These and additional proposed methodological advances will enable collection of the experimental data required to evaluate and extend the working hypothesis. The data will also furnish a quantitative baseline for evaluating aging-related neuronal changes in PR and LA, changes of the kind that could explain certain aging-related alterations in learning, memory, and mood seen in humans. Ultimately, the information gained by these studies should be pertinent to the prevention and/or treatment of age- or disease-related mental dysfunctions, including Alzheimer's disease, epilepsy, and schizophrenia.